License Plate Recognition (LPR) systems are typically employed to scan and log license plate information associated with vehicles in publically accessible areas. A typical LPR unit performs image analysis on captured images to identify the license plate number associated with each image. A typical LPR unit generates a record for each license plate number captured. The record may include any of an optical character recognition (OCR) interpretation of the captured license plate image (e.g., output in text string object format), images of the license plate number, a perspective image of the vehicle associated with the license plate number, the date and time of image capture, and the location of the LPR unit at the time of image capture. By continuing to operate each LPR unit for prolonged periods of time over a large area, the amount of aggregated LPR information grows. In addition, by combining the information generated by many LPR units, an LPR system may develop a large record of LPR information.
In one example, images captured by LPR systems at two different locations on a roadway may be analyzed to determine the average speed of a vehicle. Typically, two or more LPR systems are located a known distance apart on a particular roadway. Images captured by both systems are compared to identify image pairs associated with the same vehicle. An estimate of the average speed of the vehicle passing between the two LPR systems is computed based on the difference in time between capture of each of the pair of images and the known distance between the two different LPR systems used to capture each image.
Typically, the two LPR systems are physically separated by a relatively large distance (e.g., kilometers). Thus, the calculated average speed information may mask important details about the actual speed of the vehicle between the two LPR systems. In addition, images of the same vehicle captured by two different LPR systems must be identified to perform the estimation. Moreover, based on the aforementioned technique, two or more LPR systems installed at different locations are required to perform speed estimation.
Cost-effective improvements are desired to estimate vehicle speed based on LPR information.